Pneumatic abrasive cutting apparatus

ABSTRACT

Abrasive cutting apparatus in which a mixture of abrasive particles and a fluid, such as air, under pressure, are expelled at high speed from a nozzle, a compartmented housing being utilized to provide a working compartment connecting directly with a suction compartment, and an isolated control compartment for the abrasive reservoir or reservoirs and associated control components which are supported for removal as a unitary assembly. Means are provided for utilizing the pressurized fluid for fluffing up the abrasive powder in the reservoir to facilitate feeding to the nozzle, and to prevent clogging or packing in the reservoir. A pneumatically actuated pinch valve controls flow of air and the carried abrasive powder to the nozzle through a tubing of a material, such as latex, which prevents tunneling, and manually operable valve means provides for reservoir selection and venting.

United States Patent [191 Piet 1 June 11, 1974 PNEUMATIC ABRASIVECUTTING 3,516,204 6/1970 Kulischenko .Q 51/8 APPARATUS 3,631,631 1/1972Greenstein 51/8 [75] Inventor: Meyer Piet, Arcadia, Calif. [73]Assignee; Futurecraft Corporation, Industry,

' Calif.

[22] Filed: Nov. 1, 1971 [21] Appl. No: 194,194

[52] US. Cl. 51/12 [51] Int. Cl. B24c 3/00 [58] Field of Search 51/8,12, 11; 137/597;

[56] References Cited 7 UNITED STATES PATENTS 7 554,300 2/1896 Parker51/12 1,730,195 10/1929 Davis 51/12 2,652,093 9/1953 Burton 138/137 X2,729,917 1/1956 Gregory 51/8 2,770,924 11/1956 Mead et a1 r 51/82,888,954 6/1959 Gates 138/137 2,899,982 8/1959 Harpfer. 138/1372,938,305 5/1960 Bipes 51/12 2,971,538 2/1961 Brumbach 138/137 X3,038,449 6/1962 Murphy et a1. 137/597 X 3,514,905 6/1970 King et a1.51/12 Pea/w P6655026 SO0E66 Primary ExaminerDona1d G. Kelly AssistantExaminer-Howard N. Goldberg Attorney, Agent, or FirmWhann & McManigal [57] ABSTRACT V Abrasive cutting apparatus in which a mixture of abrasiveparticles and a fluid, such as air, under pressure, are expelled at highspeed from a nozzle, a compartmented housing being utilized to provide aworking compartment connecting directly with a suction compartment, andan isolated control compartment for the abrasive reservoir or reservoirsand associated control components which are supported for removal as aunitary assembly. Means are provided for utilizing the pressurized fluidfor fluffing up the abrasive powder in the reservoir to facilitatefeeding to the nozzle, and to prevent clogging or packing in thereservoir. A pneumatically actuated pinch valve controls flow of air andthe carried abrasive powder to the nozzle through a tubing of amaterial, such as latex, which prevents tunneling, and manually operablevalve means provides for reservoir selection and venting.

7 Claims, 12 Drawing Figures 1 PNEUMATIC ABRASIVE CUTTING APPARATUSBACKGROUND OF THE INVENTION The present invention relates broadly to thefield of abrasive cutting apparatus.

In the past, a variety of arrangements have been considered with a viewto providing more effective and dependable mixing means in abrasivecutting apparatus. In such apparatus where abrasive materials havingrelatively large particles are utilized, such as sand and the like,gravity feed of the abrasive substance into the fluid stream has beencomparatively satisfactory. However, in the case of certain types ofabrasive cutting apparatus as used in industry and dental laboratorywork, where the abrasive is composed of fine particles or is in the formof a powder, gravity feeds have not been practical for the reason thatthe abrasive substances have a tendency to become compacted and clog thepassage openings to such an extent as to make the feed very erratic andunreliable. In these cases attempts have been made to improve theoperation by providing vibratory or shaker means. However, suchexpedients have not been entirely satisfactory.

In the present invention, this problem has been greatly alleviated by aunique feeding arrangement, wherein the pressurized fluid is introducedinto the abrasive reservoir in such a manner as to fluff up the abrasivesubstance adjacent the point where the abrasive isbeing introduced intothe pressurized fluid stream for delivery to the nozzle.

Another source of trouble in the heretofore known apparatus residesin'the eroding characteristic of the abrasive, and thewearing away ofsurfaces along the conducting path traversed by the fluid entrainedabrasive. Thisproblem has been a particularly serious one whereconventional pinch valves have been used for starting and stopping theflow of the abrasive containing fluid between the feeding source and theapplicator nozzle. One of the main sources of trouble in the currentlyavailable pinch valve structures was the tunneling effect of theabrasive on the lining of the flexible tube at the operating point ofthe pinch valve as the re sult of the opening and closing of the flowline therethrough.

In the present invention, this problem has been overcome by thediscovery that latex or natural rubber were substantially impervious towear by the abrasive. By utilizing special tubing embodying a tubularcore of this material, and providing a curved surface on the pinchingmember of the valve, effective and dependable control is obtainable.

In some of the currently available equipment, trouble has developed forthe reason that the housings for the various control valveswere notproperly designed to protect the operating components from the effectsof abrasive dust which. could get into the parts and render theminoperative. This was particularly true in the case of solenoid actuatedcontrol valves which were difficult to seal. This problem has beensubstantially eliminated and the operation greatly improved by utilizingpneumatically operated valves, and by designing the housing in such away that the valves and other control components will be isolated fromthe working areas which mightcontain abrasive dust.

The above refinements as well as the incorporation of other designfeatures in the present invention has resulted in the obtainment of agreatly improved abrasive cutting apparatus which is more efficient,longer lived, dependable and easier to use than the formerly knownembodiments.

SUMMARY OF THE INVENTION The present invention relates generally toabrasive cutting apparatus, and is more particularly concerned I provedapparatusof this type which is simple of construction, easy to operateand maintain, efficient in operation, substantially free frommalfunctions, and in which the component parts are readily and easilyaccessible for inspection, replacement or repair.

A further object of the herein described invention is to provide aunique compartmented housingfor the control and other devices so as toisolate them from working areas and spaces where they might be subjectedto abrasive dust which could produce a malfunction. a

A further object is to provide albrasive cutting apparatus havingpneumatic control devices which are more easily designed to protectmoving parts from the effects of abrasive dust. i

Another object resides in the provision of improved means for mixing theabrasive substances and pressurized air or other fluid'within the supplyreservoir of the abrasive, wherein the pressurized fluid is introducedinto the reservoir in such a manner as to fluff up the abrasive powderin the area where it is to be introduced into the pressurized fluidstream for feeding to the applicator nozzle.

Still another object is to provide extremelycompact abrasive cuttingapparatus having improvedmeans for controlling the flow of pressurizedfluid and carried abrasive to an applicator nozzle, and in which thecontrolling means comprises a pneumatically controlled pinch valve ofunique design, and in which abrasive tunneling will be substantiallyeliminated.

Also, still another object is to provide in apparatus of the hereindescribed type, having; provision for the use of several types ofabrasive, improved selector valve means for the selection of theabrasive to be used, and for venting the supply reservoir of thenonselected abrasive.

Further objects and advantages of the invention will be brought out inthe following part of the specification, wherein detailed description isfor the purpose of fully disclosing a preferred embodiment as well asseveral modifications of the invention without placing limitationsthereon.

BRIEF DESCRIPTION OF THE DRAWINGS Referring to the accompanyingdrawings, which are FIG. 3 is a fragmentary section showing features ofthe internal wall structure of the housing, taken substantially on line33 of FIG. 2;

FIG. 4 is a fragmentary elevational view showing features of the housingstructure, as seen from line 4-4 of FIG. 2;

FIG. 5 is a view schematically illustrating one embodiment of theinvention which includes selective dual supplies of abrasive substances;

FIG. 6 is a similar view in which a single abrasive supply is provided;I

FIG. 7 is an enlarged vertical section through an abrasive reservoir,and showing one arrangement for feeding the abrasive substance into afluid stream;

FIG. 8 is a fragmentary view, in section, showing details of a reservoirclosure cap containing a desiccant and vent valve;

FIG. 9 is a plan view, partly in section, of a pinch valve as embodiedin the herein described invention;

FIG. 10 is a fragmentary section showing details of the cooperativerelationship of certain parts of the pinch valve, taken substantially online 10-10 of FIG.

FIG. 11 is a fragmentary sectional view of a bottom portion of anabrasive reservoir showing a modified arrangement for abrasive feed; and

FIG. 12 is a similar view showing another modification of the abrasivefeed.

DESCRIPTION OF A PREFERRED AND SEVERAL EMBODIMENTS Referring morespecifically to the drawings, there is illustrated in FIG. 1 anapparatus constructed and embodying the features of the presentinvention, wherein the operative components and devices are containedwithin a housing structure as generally indicated by the numeral 10.This structure is shown as a box-like container of fabricated sheetmetal or other suitable material to provide a planar bottom wall 11 fromwhich there extends a right angled rear wall 12 and front wall 13 whichis of less width and less height than the rear wall. Forwardly extendingon each side of the rear wall are right angled upstanding side wallportions Ma and 15a, which respectively connect with integrally formedside wall portions 14b and 15b which are in converging relation andconnect with the respective sides of the front wall 13. As best shown inFIG. 2, the top wall of the housing comprises an integrally formedportion- 16a which extends parallel to the bottom wall 1 1, and aportion 16b which is forwardly inclined downwardly towards the top ofthe front wall 13, and connects'with a viewing window structure asgenerally indicated at 17. The window tapers towards the wall 13 and hasa configuration conforming to that of the side walls. The window isconnected by a hinge structure 18 to the wall portion 16b, and in itsclosed position is substantially coplanar with that of the wall portion16b. At its forward edge, provision is made for releasably securing thewindow in a closed position by means of a suitable latch 19.

lnteriorly, the housing as described above is compartmented to provide aforward work chamber as generally indicated by the numeral 20, a bottomrear suction chamber 21 and an associated upper control chamber As shownin FIGS. 1 and 2, the work chamber is in communication with the suctionchamber 21 through a perforated wall partition 23 so as to effectremoval of waste abrasive materials as the result of a working operationperformed in the work chamber. The work chamber wallportions 14b and 15bare shown as containing the usual hand ports 24a and 24b, respectively,while the window 17 permits the operator to view the work operationbeing carried on. Illumination is provided in the work chamber by meansof a suitable fluorescent light source as generally indicated at 25, andhaving appropriate supply conductors 26 carried through an insulatinggrommet 27 in the wall 23, to a control switch 28 and thence through aninsulating grommet 29 in the rear wall 12 to the housing exterior whereit may be connected with a suitable electric supply source.

The suction chamber 21 is arranged to be selectively connected with asuitable vacuum source by means of a vacuum hose, as indicated at 30. Tofacilitate right or left hand connections of the hose to the suctionchamber, openings 3131 are provided in the opposite side walls of thechamber, a closure plug (not shown) being used to close the opening 31that is not being used.

The control chamber 22 is separated from the work chamber 20 and thesuction chamber 2] by means of an isolating solid partition wall 32 inorder that the abrasive storage and control components will be shieldedwith respect to abrasive dust which might be prevalent in the workchamber and suction chamber.

This is one of the important features of the invention, since itminimizes malfunction due to this abrasive dust getting into theoperating parts of the control devices.

In order to provide ready access to the control devices for checking,replacement or repair, a further feature of the invention is to mountthese various components on the top wall portions 16a and 16b which arearranged to provide aremovable closure for the control chamber, wherebythese components may be removed as a unit. As a part of this feature, itwill be observed in FIG. 4, that the wall portion 16a is provided with arear extension 16c which covers an opening 32' in the back wall 12 toaccommodate a connection fitting 33 whereby the components may beconnected with a suitable pressure source of fluid supply, as well as aprotective entrance grommet 34 for bringing in the flexible pair ofconduits 35 from a suitable foot valve control device as generallyindicated at 36 by means of which the technician controls the supply ofabrasive and fluid mixture to one of more handpiece nozzles as indicatedat 37 (FIG. 2) this nozzle being supplied through an appropriateflexible conduit 38 which is carried through a protective grommet 39 inthe wall 32 into the control chamber where it is connected with suitablecontrol devices as will hereinafter be explained in detail. When thehandpiece nozzle is not being used, it can be positioned in a tubularhandpiece support 40 secured onto the wall partition 23.

Pneumatically controlled and operated apparatus of the present inventionmay take either of two forms as schematically illustrated in FIGS. 5 and6 respectively. Basically the operation is the same in each case. In thearrangement shown in FIG. 5, provision is made for utilizing twodifferent abrasives which are contained in separate supply reservoirs asindicated at 41 and 42 respectively. The reservoir 41 bears the legendGold" and contains an abrasive which is particularly adapted for workingon the material gold, while the reservoir 42 is labled Porcelain andcontains an abrasive which is suitable for working on porcelain. Theapparatus is not limited to the use of abrasives for these particularmate rials, and it is to be understood that they are mentioned merelyfor the reason that the disclosed apparatus is primarily used inconnection with dental laboratory work. Pressurized fluid such as air ora neutral gas is supplied to the apparatus from a suitable externalsource which is introduced through a conventional filter 43 coupled tothe connection fitting 33 from whence it is fed into a conventionalpressure regulator 44 having a manually adjustable knob 44', as shown inFIG. 1, which is readily accessible on the top wall portion 16b whichserves as a control panel. By means of this knob, the operatingpressures are adjustable and readable on a pressure gauge 45 which isalso on the control panel. Usually the operating pressures will be ofthe order of 120 P.S.l. Fluid pressure is distributed from the regulator44 to the abrasive reservoirs 41 and 42 through individual supplyconduits 46 and 47, these conduits being carried through a selector andventing valve 48 of conventional construction, and provided with amanually actuating knob 48 positioned on the control panel portion ofthehousing. This knob is operable to selectively connect the inputconduits 46 and 47 with the desired reservoir, and also is positionableso as to vent the reservoirs to relieve pressure therein during times ofnonuse.

The pressurized air or other fluid supplied to the abrasive reservoirsis mixed with the abrasive therein as will hereinafter be discussed indetail, and then delivered through separate outlet conduits 49 or 50 tothe selected handpiece 37 depending upon which reservoir is being used.

In the arrangement shown in FIG. 5, which utilizes two abrasivereservoirs, the flow through the output conduits 49 and 50 to thehandpiece nozzles is controlled by a pneumatically actuated pinch valveas generally indicated at 51 which will subsequently be described indetail, but basically comprises a structure which is normally urged to anon-pinching position with reference to associated portions of theconduits 49 and 50, but upon energization by pressure fluid suppliedthrough a conduit 52 will be actuated into a pinching position in whichflow will be terminated to the handpiece nozzles. Actuation of the pinchvalve is controlled by means of the foot valve 36 as shown in FIG. 1,and which is diagrammatically illustrated in FIGS. 5 and 6 as comprisinga casing 53 which is constructed to provide an internal cavity 54 withinwhich there is reciprocably mounted a valve member 55 which is moveablebetween opposed valve seats 56 and 57, the first of these controllingflow between an inlet connection 58 and the cavity, and the secondcontrolling flow between a vent passage 59 and the cavity. The inletconnection 58 is in communication by a conduit 60 with the regulator'44from which pressurized fluid is obtained. The internal cavity 54 is incommunication with an inletou tlet connection 61 which is incommunication with the conduit 52 connected to the pinch valve 51. Aspring 62 normally maintains the valve member SS in a position closingthe vent passage 59, and at which time the valve member will be unseatedwith respect to the valve seat 56 so as to establish flow of pressurizedfluid from the inlet connection 58 to the inlet-outlet connection 61 toenergize the pinch valve and move it to pinching or closed positioncutting off flow to the connected handpiece nozzles. When it is de siredto open the pinch valve 51 so as to provide flow to a selected nozzle37, the valve may be actuated by manually engaging a projecting sternportion 63 and moving it in a direction to overcome the action of thespring 62 and move the valve member into engagement with the seat 56.This cuts off the supply of pressurized fluid to the pinch valve andconnects the cavity 54 with the vent passage so as to relieve thepressure in the pinch valve and enable it to move to its normal openposition. The foot valve as shown in FIG. 6 is of the same constructionand operates in the same manner as the one shown in FIG. 5. In thearrangement of FIG. 6,

however, the valve 48 acts only as a selector or connecting valve forthe reservoir 42 and does not perform a venting operation in this case.For this reason it is necessary to provide a normally closed vent valve64, as will be subsequentlydescribed in detail, this valve being mountedin a removable closure cap 65 of the reservoir. This vent valve is notnecessary for the caps of the reservoirs shown in FIG. 5, since theventing of these reservoirs is accomplished through the valve 48.

It will be noted that the reservoirs 41 and 42, 'as shown in FIG. 1, aremounted on'the top wall portion 16a which provides the cover for thecontrol chamber. For explaining the means utilized for the mixing of theabrasive in the reservoir arrangement shown in FIGS. 5 and 6, referenceis made to the details of construction as shown in FIG. 7. As thereshown, the reservoir 42 contains a quantity of the abrasive powder asindicated by the numeral 66 and which extends to an upper level asgenerally indicated at 67. The pressurized fluid inlet conduit 47 isshown as being connected at one side of the bottom of the reservoir bymeans of a fitting which includes a reverse flow check valve asgenerally indicated by the numeral 68. The outlet conduit 50 isconnected with a central standpipe 69 which extends through the bottomof the reservoir and has an upper most end'which is shown as extendingabove the abrasive level 67. The upper end is closed by a plug 70 toprevent loading the standpipe tube with abrasive powder when thereservoir is being filled or replenished.

Flow openings as indicated at 71 are provided below the plug, theseopenings being normally disposed in the space above the abrasive level67.. Adjacent the bottom end of the reservoir, the standpipe is providedwith a plurality of pickup holes or openings as indicated at 72'. Itwill be noted that the openings 72 are positioned above the inlet flowof airfrom the conduit 47 into the bottom of the reservoir. It ispreferable that more than one opening 72 be provided since itsorientation with respect to the air inlet is critical. For example, if asingle pickup hole faces the air inlet, it will receive an abnormalblast of air-abrasive, which will throw the airabrasive mixture out ofbalance, or undue erosion could result.

It is also important that means be provided to keep moisture out of theabrasive powder, and for this purpose there is provided on the innersurface of the cap 65 a removably mounted cup member 73 which is adaptedto support a desiccant pill 74 in an operative position in the space atthe top of the reservoir, communicating openings 75 being provided inthe cup walls.

The operationof the arrangement described above will now be considered.With pressure fluid applied through the conduit 47, the pressure will besubstantially equalized within. the reservoir, when the flow to thebandpiece nozzle is cut off by the pinch valve. Upon opening the pinchvalve by actuation of the foot valve control, flow will be establishedthrough the conduit 50 to the handpiecenozzle, and as a result thepressure at the upper end of the reservoir container will be decreased.The air now entering the reservoir from the conduit 47 will act to raiseand fluff up the abrasive powder particularly at the lower end of thereservoir in the area of the pickup openings 72 as generally indicatedin phantom lines by the numeral 76 so that as air flows downwardlythrough the standpipe 69 from the space at the upper end of thereservoir, abrasive will be asperated through the openings 72 into theair stream and thus carried to the handpiece nozzle. By placing theopenings 72 above the entering air stream, compacting and clogging ofthe abrasive powder in the pickup area will be effectively prevented andmore dependable and efflcient operation obtained.

In the modified arrangement as shown in FIG. 1 1, the inlet fluid fromthe conduit 47 is carried to an annular discharge nozzle or opening 77which surrounds the lower end of the standpipe and ejects a cylindricalair stream upwardly past the pickup openings 72. This arrangement hasthe advantage in that a uniform lifting and fluffing of the abrasivearound the pickup openings is obtained and a condition produced in whichthe possibility of stagnant abrasive areas is reduced to a minimum.

The modified arrangement shown in FIG. 12, instead of utilizing avertical standpipe, is arranged with a horizontal pipe 69 which ispreferably supported above the abrasive level67 with pickup holes 72therein at the center of the'reservoir. In this arrangement, instead offirst conducting the gas through the abrasive material prior to enteringthe tube having the pickup holes therein, the air isconducted through abranch line 78 directly from the inlet of conduit 47 to an inlet end 79of the tube 69, the normally open end of this tube being shut off bysuitable closure means 80. In addition, the flow of fluid from theconduit 47 t the nozzle outlet 77, which is the same as previouslydescribed for FIG. 11, may be varied by means of an adjustable needlevalve structure as generally indicated at 81. This arrangement has theadvantage of being more versatile and permitting a regulatory control ofthe fluid stream from the nozzle 77 for causing fluffing of the abrasivesubstance. This is of particular advantage when using abrasives ofdifferent size characteristics.

Referring to FIG. 8, the details of the structure of the vent valve 64are shown. The upper cap wall is provided with a vent opening 82 throughwhich a valve stem 83 extends. The innermost end of this valve stemcarries a sealing ring 84 having valving association with the opening82, the sealing ring being retained on the stem by a snap ring 85. Theouter end of the stem 83 is formed to provide digitally engageablebutton 86. A compression spring 87 having one end in engagement with theunderside of the button and its other end in engagement with a flange inthe cap wall, operates to normally urge the sealing ring 84 into a valveclosed position. With a valve as just described, it is a simple matterto vent the abrasive reservoir; which may be done by manually depressingthe button 86. In order to prevent the dissemination of abrasive powderfrom the reservoir during a venting operation, a fine screen of theorder of 400 mesh, as indicated by the numeral 88, is appropriatelymounted in the venting path.

The details of construction of the pinch valve 51 will now beconsidered, reference being hadto FIGS. 5 and 10. As there disclosed,this valve comprises a frame structure 89 that is fabricated with a headportion 90 provided with an elongate open-sided groove or passage 91which is adapted to receive in side-by-side relation the conduitstructures 49 and 50 leading to the handpiece nozzles 37-37. Theseconduits are of special design and comprise in each case a tubing core92 of latex or natural rubber which have been found to be substantiallyimpervious to wear by the abrasive. This core is encased within abraided nylon sheath as indicated at 93, and where the conduits arecarried through the passage 91, the conduits are surrounded by aprotective plastic tube 94 in each case which is longitudinally split asindicated at 94'. The conduit assemblies are retained within the passageby means of a front retaining plate 95 which is secured by means ofappropri ate screws 96. In communication with the passage 91, there isprovided a lateral opening 97 within which there is reciprocably movablypositioned a pinch block member 98. This block as shown in FIG. 9 isprovided with a transversely curved surface 99 for engaging with theconduit assemblies which include the conduits 49 and 50. The oppositeside of the block 98 is provided with a recess 100 which is adapted toloosely receive the outer end of an actuating stem 101 having connectionwith a piston 102 operatively reciprocal within an associated cylinder103 that is closed at one end by a cap member 104 which carries'a guidebushing 105 for the stem 101. The piston is provided with a cup seal 106which serves to seal the piston when fluid pressure is applied throughan inlet 108 to the opposite end of the cylinder to move the block 98into pinching position with respect to the conduit assemblies in thepassage 91. A compression spring 107, which extends between the pistonand an abutment shoulder formed in the guide bushing 105, normallyurgesthe block 98 to a non-pinching position. The upper end of thecylinder, as shown in FIG. 9, is connected with atmosphere through avent opening l09 containing a fine mesh screen 110 which prevents theentrance of any abrasive dust which might be within the control chamber.

The pinch valve structure having the design as described above, has beenfound to be very effective and trouble free, and especially free oftunneling of the materials constituting the cores of the conduits 49 and50. Moreover, the utilization of pneumatic actuating means for thisvalve is also trouble free as compared to electrically actuated valveswhich have been heretofore utilized.

From the foregoing description and drawings, it will be clearly evidentthat the delineated objects and features of the invention will beaccomplished.

Various modifications may suggest themselves to those skilled in the artwithout departing from the spirit of the disclosed invention, and,hence, it is not wished to be restricted to the specific form shown oruses mentioned except to the extent indicated in the appended claims.

I claim:

1. Abrasive cutting apparatus, comprising:

a. a source of pressurized fluid;

b. an assembly comprising a reservoir containing an abrasive substance,said reservoir having an inlet connectible with said source and beingpositioned to discharge fluid into said abrasive substance in a bottomportion of said reservoir, and outlet means including a fluid flowpassage in a tubular member, a portion of which is positioned in a topspace of said reservoir, and an inlet opening in said tubular member foradmission of the abrasive substance into said fluid flow passage;

discharge nozzle means connected with said outlet means;

d. pneumatic actuated valve means for controlling flow to said dischargenozzle; and a foot valve for controlling the actuation of said valvemeans including:

a casing having an internal cavity communicating with a vent opening;

a pressurized fluid inlet connected with an inletoutlet connectionoperatively connected with said valve means;

a valve structure in said cavity normally urged to one position closingsaid vent opening and establishing flow between said inlet and saidinletoutlet connection, and upon manualactuation to another positioninterrupting flow between said inlet and said inlet-outlet connectionand connecting said inlet-outlet connection with said vent opening.

2. Abrasive cutting apparatus, comprising: a. a source of pressurizedfluid; b. an assembly comprising a reservoir containing an abrasivesubstance, said reservoir having an inlet connectible with said sourceand being positioned to discharge fluid into said abrasive substance ina bottom portion of said reservoir, and outlet means including a fluidflow passage in a tubular member, a portion of which is positioned in atop space of said reservoir, and'an inlet-opening in said tubular memberfor admission of the abrasive substance into said fluidflow passage;

discharge nozzle means connected with said outlet means by a flexibletubing structure;

d. valve means for controlling flow to said discharge nozzle including ablock member reciprocably movable into pinching and non-pinchingrelation with respect to said flexible tubing structure; and a pneumaticactuator comprising:

a cylinder and a piston reciprocable in said cylinder, said pistonhaving a stem with an outer end positioned within a receiving socket ofsaid block member;

spring means for moving said piston in a direction enabling movement ofsaid block member into said non-pinching relation;

and a connection with said cylinder for supplying pressurized fluid tomove said piston in a direction to carry said block member into saidpinching relation.

. Abrasive cutting apparatus, comprising: a source of pressurized fluid;

t b. an assembly comprising a reservoir containing an abrasivesubstance, said reservoir having an inlet connectable with said sourceand being positioned in a bottom portion of said reservoir, and outletmeans including a fluid flow passage in a horizontally extending tubularmember positioned in a top space at the upper end of said reservoirabove the abrasive and with an input end connecting the fluid flowpassage with said source of pressurized fluid, and an inlet opening insaid tubular member for admission of the abrasive substance into saidfluid flow passage, said reservoir inlet having a fluid discharge axisdirected generally into the abrasive substance below the inlet openingin said tubular member;

c. a reverse flow check-valve between said source, the reservoir inlet,and said input end of said fluid flow passage;

d. discharge nozzle means connected with said outlet means; and

e. valve means for controlling the flow to said discharge nozzle.

4. Abrasive cutting apparatus according to claim 3, including a flowadjusting needle valve between said check valve and said reservoirinlet.

5. Abrasive cutting apparatus, comprising:

a. a source of pressurized fluid;

b. an assembly comprising a reservoir containing an abrasive substance,a removable cap closure member, a reservoir inlet connectable with saidsource and being positioned in a bottom portion of said reservoir, andoutlet means including a fluid flow passage in a tubular member, aportion of which is positioned in a top space of said reservoir, and aninlet opening in said tubular member for admission of the abrasivesubstance into said fluid flow passage, said reservoir inlet having afluid discharge axis directed generally into the abrasive substancesurrounding the inlet opening in said tubular member;

desiccant means within said reservoir carried by and being removablewith said cap member;

d. discharge nozzle means connected with said outlet means; and

e. valve means for controlling flow to said discharge nozzle.

6. Abrasive cutting apparatus according to claim 5,

wherein the cap closure has a vent opening normally closed by valvemeans having an exteriorly manually tioned at the bottom portion of saidreservoir.

1. Abrasive cutting apparatus, comprising: a. a source of pressurizedfluid; b. an assembly comprising a reservoir containing an abrasivesubstance, said reservoir having an inlet connectible with said sourceand being positioned to discharge fluid into said abrasive substance ina bottom portion of said reservoir, and outlet means including a fluidflow passage in a tubular member, a portion of which is positioned in atop space of said reservoir, and an inlet opening in said tubular memberfor admission of the abrasive substance into said fluid flow passage; c.discharge nozzle means connected with said outlet means; d. pneumaticactuated valve means for controlling flow to said discharge nozzle; ande. a foot valve for controlling the actuation of said valve meansincluding: a casing having an internal cavity communicating with a ventopening; a pressurized fluid inlet connected with an inlet-outletconnection operatively connected with said valve means; a valvestructure in said cavity normally urged to one position closing saidvent opening and establishing flow between said inlet and saidinlet-outlet connection, and upon manual actuation to another positioninterrupting flow between said inlet and said inlet-outlet connectionand connecting said inlet-outlet connection with said vent opening. 2.Abrasive cutting apparatus, comprising: a. a source of pressurizedfluid; b. an assembly comprising a reservoir containing an abrasivesubstance, said reservoir having an inlet connectible with said sourceand being positioned to discharge fluid into said abrasive substance ina bottom portion of said reservoir, and outlet means including a fluidflow passage in a tubular member, a portion of which is positioned in atop space of said reservoir, and an inlet opening in said tubular memberfor admission of the abrasive substance into said fluid flow passage; c.discharge nozzle means connected with said outlet means by a flexibletubing structure; d. valve means for controlling flow to said dischargenozzle including a block member reciprocably movable into pinching andnon-pinching relation with respect to said flexible tubing structure;and e. a pneumatic actuator comprising: a cylinder and a pistonreciprocable in said cylinder, said piston having a stem with an outerend positioned within a receiving socket of said block member; springmeans for moving said piston in a direction enabling movement of saidblock member into said non-pinching relation; and a connection with saidcylinder for supplying pressurized fluid to move said piston in adirection to carry said block member into said pinching relation. 3.Abrasive cutting apparatus, comprising: a. a source of pressurizedfluid; b. an assembly comprising a reservoir containing an abrasivesubstance, said reservoir having an inlet connectable with said sourceand being positioned in a bottom portion of said reservoir, and outletmeans including a fluid flow passage in a horizontally extending tubularmember positioned in a top space at the upper end of said reservoirabove the abrasive and with an input end connecting the fluid Flowpassage with said source of pressurized fluid, and an inlet opening insaid tubular member for admission of the abrasive substance into saidfluid flow passage, said reservoir inlet having a fluid discharge axisdirected generally into the abrasive substance below the inlet openingin said tubular member; c. a reverse flow check-valve between saidsource, the reservoir inlet, and said input end of said fluid flowpassage; d. discharge nozzle means connected with said outlet means; ande. valve means for controlling the flow to said discharge nozzle. 4.Abrasive cutting apparatus according to claim 3, including a flowadjusting needle valve between said check valve and said reservoirinlet.
 5. Abrasive cutting apparatus, comprising: a. a source ofpressurized fluid; b. an assembly comprising a reservoir containing anabrasive substance, a removable cap closure member, a reservoir inletconnectable with said source and being positioned in a bottom portion ofsaid reservoir, and outlet means including a fluid flow passage in atubular member, a portion of which is positioned in a top space of saidreservoir, and an inlet opening in said tubular member for admission ofthe abrasive substance into said fluid flow passage, said reservoirinlet having a fluid discharge axis directed generally into the abrasivesubstance surrounding the inlet opening in said tubular member; c.desiccant means within said reservoir carried by and being removablewith said cap member; d. discharge nozzle means connected with saidoutlet means; and e. valve means for controlling flow to said dischargenozzle.
 6. Abrasive cutting apparatus according to claim 5, wherein thecap closure has a vent opening normally closed by valve means having anexteriorly manually operable actuator for moving the valve means to openposition with respect to said vent opening.
 7. Abrasive cuttingapparatus according to claim 5, wherein the tubular member of the outletmeans extends vertically of the reservoir and has an opening at itsupper end for receiving fluid discharged from said reservoir inlet afterit has passed through the abrasive substance, and the inlet in saidtubular member is positioned at the bottom portion of said reservoir.